This invention relates to fluid metering rolls, and in particular, to anilox rollers used in printing processes.
Anilox rollers are fluid metering rollers and are used in printing presses and have the function of precisely metering the amount of ink that is deposited onto a printing plate printing roller, or the like. The anilox roller has an exterior surface formed with outward opening metering cells. The anilox roller picks up liquid ink from an ink source and deposits the ink on a printing plate, printing roller, or the like, in discrete increments, the quantity deposited by each cell being controlled within precise tolerances across the entire surface of the printing plate, printing roller, or the like. This result is affected by the anilox roller having a multiplicity of closely-spaced, i.e., up to 1,000 or more, cells per lineal inch, the cells having virtually identical volumetric capacities.
Anilox rollers have been in use for many years. A typical anilox roller is comprised of a cylindrical metal body (usually steel) and rigidly fixed journals (typically, welded or shrink fit construction) through which the roller is mounted on bearings or a drive system. The surface of the metal roller is then modified to contain many (millions) of very small cells in which ink can be retained. The cells are typically made by either mechanically engraving the roller or by coating the metal roller with ceramic and engraving the cells with a laser. Metal rollers have many characteristics which are undesirable. These characteristics include heavy weight and high rotating inertia. They also exhibit poor vibration attenuation.
As an alternative to metal anilox rollers, some companies have manufactured anilox rollers using a carbon fiber reinforced composite material rather than metal as the roller body. Examples of this may be seen in U.S. Pat. Nos. 6,240,639 and 5,857,950. An anilox roller made out of a carbon fiber reinforced composite typically weighs substantially less (up to 50% less) and has a lower rotating inertia (up to 80% less) than its metal equivalent. A carbon fiber anilox roller is typically made by coating a carbon fiber roller body with ceramic and subsequently laser engraving the surface.
Although typical carbon fiber anilox rollers provide rollers that weigh considerably less than and have a considerably lower rotating inertia than their metal counterparts, they do have their own significant disadvantages. Carbon fiber anilox rollers typically do not last as long as their steel counterparts. The bond between the ceramic coating and the composite roller body is generally not as strong as that between a ceramic coating and a metal body. Consequently, the ceramic coating on a carbon fiber anilox base is known to prematurely flake off. Carbon fiber anilox rollers also cost two to three times as much as metal anilox rollers. Both metal and carbon fiber anilox rollers can only be refinished (reground and recoated) a limited number of times, typically two to five times.
Due to the corrosive nature of chemicals that are employed in the printing process and the anilox roller cleaning process, anilox rollers generally require refurbishing after extended period of use. Refurbishment of a metal anilox roller generally involves grinding off the ceramic coating or engraving surface and a small amount of metal below the coating in order to obtain a new, clean surface. Refurbishment of a prior art carbon fiber anilox roller involves stripping of the ceramic coating by various means and removal of a small layer of carbon fiber composite in order to obtain a new, clean surface. Metal anilox rollers can generally be refurbished about three times before they must be discarded. Carbon fiber anilox rollers can, in general, be refurbished more times than metal anilox rollers, but the number of times they can be refurbished is still very limited.
The present invention addresses the problem of prior art anilox rollers by providing a metal-sleeved carbon fiber anilox roller base which is a hybrid between the prior art metal anilox roller base and the prior art carbon fiber anilox roller base. The present invention is an improvement over both technologies. The present invention is comprised of a carbon fiber composite cylinder over which a metal sleeve is fitted. Metal journals, journal headers, or end caps are installed into the invention ends. A ceramic coating is then typically added to the metal sleeve external surface. The sleeve is subsequently machined to the precise dimensions required of an anilox roller.
The metal-sleeved carbon fiber anilox roller combines the light weight and low inertia characteristics of the carbon fiber anilox roller base with the durability and ease of processing of the metal anilox roller base. The metal-sleeved carbon fiber anilox roller can be made into an anilox roller by any of the dozens of companies that manufacture metal anilox rollers from metal anilox roller bases. No change in processing is required. The ceramic coating adheres as well to the metal-sleeved roller base as it does to a standard metal anilox roller base. The present invention allows any company that manufactures metal anilox rollers to now participate in the lightweight, low inertia anilox roller market, and provides a unique solution to the problem of poor adherence between carbon fiber composites and ceramic coatings.
Refurbishment of a metal-sleeved anilox roller is carried out via the same means used for a metal anilox roller. After several refurbishments, the remaining sleeve material becomes too thin to grind effectively. When the sleeve material becomes too thin to regrind, the sleeve is removed and a new sleeve is installed saving considerable cost over a replacement roller, be it metal or carbon fiber composite. The resulting refurbished roller is generally indistinguishable from the original anilox roller. Replacement of the metal sleeve thereby permits an unlimited number of refurbishments of a metal-sleeved carbon fiber anilox roller. This provides an additional advantage of the present invention over prior art anilox rollers because the cost of resleeving is less than the cost of a new metal roller base or a carbon fiber anilox roller base.
These together with other objects of the invention, along with various features of novelty which characterize the invention, are pointed out with particularity in this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention.